Interproximal reduction planning

ABSTRACT

The present disclosure includes computing device related, systems, and methods for IPR planning as described herein. One method includes identifying a first tooth and a second tooth in a digital dental model with an overlap in a target final position in a treatment plan and identifying a reference line on each of the first tooth and the second tooth; revising the treatment plan wherein a position of each of the first tooth and the second tooth is determined in which the reference line of each of the first tooth and the second tooth are aligned and the first tooth and second tooth are not overlapping; and prescribing IPR based on the determined position of each of the first tooth and the second tooth.

BACKGROUND

The present disclosure is related generally to the field of dentaltreatment. More particularly, the present disclosure relates tointerproximal reduction planning.

Many dental treatments involve repositioning misaligned teeth andchanging bite configurations for improved cosmetic appearance and dentalfunction. Orthodontic repositioning can be accomplished, for example,through a dental process that uses one or more removable positioningappliances for realigning teeth.

Such appliances may utilize a shell of material having resilientproperties, referred to as an “aligner” that generally conforms to apatient's teeth but is slightly out of alignment with the initial toothconfiguration. Placement of an appliance over the teeth can providecontrolled forces in specific locations to gradually move the teeth intoa new configuration. Repetition of this process with successiveappliances in progressive configurations can move the teeth through aseries of intermediate arrangements to a final desired arrangement.

Repositioning a patient's teeth may result in residual crowding ofadjacent teeth due to insufficient space within the patient's mouth.This residual crowding can impede complete tooth alignment. In somesituations it may be possible to remove a small portion of a tooth, orportions of two adjacent teeth, in order to make the teeth fit withinthe space available. The removal of material causing the overlap of thecrowded teeth must be treated by the treatment professional by removingmaterial from the surface of one or more teeth in a process calledinterproximal reduction (IPR). During an IPR procedure, a small amountof enamel thickness on the surface of the teeth is removed to reduce themesial-distal width and space requirements for the tooth.

One problem experienced during dental treatment is the determination bythe treatment professional of whether an IPR procedure is necessary andthe timing of IPR within the treatment. If the IPR procedure isconducted in a stage of the treatment that is too early or too late, thetreatment professional may have poor access to the surfaces of the oneor more teeth intended to be removed. Further, the treatmentprofessional may inaccurately remove material from the surface of thetooth resulting in an undesired tooth shape, a tooth surface that doesnot fit properly against another tooth, and potentially having toperform additional IPR procedures and/or other procedures to fix theoverlap or newly created underlap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an example of a digital dental model according toone or more embodiments of the present disclosure.

FIG. 1B illustrates an example of a target digital dental modelaccording to one or more embodiments of the present disclosure.

FIG. 1C illustrates an example of a revised target digital dental modelaccording to one or more embodiments of the present disclosure.

FIGS. 2A-2B illustrate examples of a ridge endpoint reference line oneach of a first tooth and a second tooth according to one or moreembodiments of the present disclosure.

FIG. 2C illustrates an example of a y-axis reference line on each of afirst tooth and a second tooth according to one or more embodiments ofthe present disclosure.

FIG. 3 is a flow chart illustrating an example of a process for IPRplanning according to one or more embodiments of the present disclosure.

FIG. 4 illustrates an example of a method for IPR planning according toone or more embodiments of the present disclosure.

FIG. 5 illustrates an example of a system for IPR planning according toone or more embodiments of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure include computing device related,system, and method embodiments for interproximal reduction planning. Forexample, one or more embodiments include a computing device implementedmethod that includes identifying a first tooth and a second tooth in adigital dental model with an overlap in a target position in a treatmentplan, identifying a reference line on each of the first tooth and thesecond tooth, revising the treatment plan wherein a position of each ofthe first tooth and the second tooth is determined in which thereference line of the first tooth and the reference line of the secondtooth are aligned and the first tooth and the second tooth are notoverlapping, and prescribing interproximal reduction based on thedetermined position of each of the first tooth and the second tooth.

In the following detailed description of the present disclosure,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration how a number of embodimentsof the disclosure may be practiced. These embodiments are described insufficient detail to enable those of ordinary skill in the art topractice a number of embodiments of this disclosure, and it is to beunderstood that other embodiments may be utilized and that changes maybe made without departing from the scope of the present disclosure.

As will be appreciated, elements shown in the various embodiments hereincan be added, exchanged, and/or eliminated so as to provide a number ofadditional embodiments of the present disclosure. In addition, as willbe appreciated, the proportion and the relative scale of the elementsprovided in the figures are intended to illustrate the embodiments ofthe present disclosure, and should not be taken in a limiting sense. Asused herein, “a”, “at least one”, “a number of” something can refer toone or more such things.

Although the overarching term “orthodontics” is used herein, the presentdisclosure may relate to treatments of an orthognathic nature. Forexample, in cases including treatment of a patient's underlying skeletalstructure, teeth may be rearranged by surgically repositioningunderlying bones that hold the teeth in order to achieve a desired finalbite arrangement. In both orthodontic and orthognathic treatmentapproaches, alignment of the teeth may be evaluated pre-, mid-, and/orpost-treatment.

Treatment professionals, such as a clinician, typically select atreatment plan for a patient's teeth based upon experience with certaintypes of physical features and/or appliances. In some embodiments, adental treatment plan can include orthodontic treatment planningfunctions and/or appliances. IPR procedures are often left to be done atthe end of a dental treatment, however, there may not be enough space toproperly align the teeth at this point in the treatment.

IPR planning within a dental treatment plan can be beneficial, forexample, in that planning for IPR can consider the ease of performingIPR. The planning of IPR can result in more accurate access to the IPRregions as compared to non-planning for IPR, more accurate removal ofthe IPR regions as compared to non-planning for IPR, and the eliminationof additional procedures to fix errors caused by inaccurate IPR timing,among other benefits.

In various embodiments, with the use of computer device executableinstructions, a treatment professional can establish a treatment planhaving a target position for a number of teeth of a particular patient.With this target position in mind, a first tooth and a second toothneeding IPR can be identified and IPR can be virtually planned at apoint during the process of moving the teeth to the target position thatis desirable for performing IPR.

Digital dental models from a scan of a patient's dentition can beprovided with computer-aided design and/or manufacturing systems,including tooth-treatment systems. A digital dental model representingan initial tooth arrangement may be obtained in a variety of ways.

For example, the patient's teeth may be imaged to obtain digital datausing direct and/or indirect structured light, X-rays, three-dimensionalX-rays, lasers, destructive scanning, computer-aided tomographic imagesor data sets, magnetic resonance images, intra-oral scanning technology,photographic reconstruction, and/or other imaging techniques. Thedigital dental model can include an entire mouth tooth arrangement,some, but not all teeth in the mouth, and/or it can include a singletooth.

A positive model and/or negative impression of the patient's teeth or atooth may be scanned using an X-ray, laser scanner, destructive scanner,structured light, and/or other range acquisition system to produce theinitial digital dental model. The data set produced by the rangeacquisition system may be converted to other formats to be compatiblewith the software which is used for manipulating images within the dataset, as described herein.

Referring now to FIG. 1A, there is illustrated an example of a digitaldental model 100 according to one or more embodiments of the presentdisclosure. As described herein, the digital dental model 100 can beobtained prior to treatment or at an intermediate state of treatment(e.g., before treatment has been completed). The digital dental model100 can include an initial position of a first tooth 101 and a secondtooth 102 or a number of teeth.

FIG. 1B illustrates a target digital dental model 104 according to oneor more embodiments of the present disclosure. The target digital dentalmodel 104 can be created by modifying the digital dental model 100according to one or more treatment goals. The target digital dentalmodel 104 can include a target position in a treatment plan of a firsttooth 101 and a second tooth 102 and a target position of a number ofteeth, for example. The one or more treatment goals can be case-specific(e.g., specific to the particular patient on which the digital dentalmodel 100 was based).

In some embodiments, a first tooth 101 and a second tooth 102 can beidentified in the digital dental model 100 with an overlap 103 in atarget position in a treatment plan. An overlap 103 can include anoverlap with a neighboring tooth 102 along an arch of the target digitaldental model 104 and a potential collision in the target position with aneighboring tooth 102, among many others. An overlap 103 that can beremedied through IPR can be approximately 0.50 millimeters, for example.For instance, in such an example, approximately 0.25 millimeters of thefirst tooth 101 and 0.25 millimeters of the second tooth 102 can beremoved via an IPR procedure. In some IPR procedures, the amount oftooth material removed can be different for two adjacent teeth (e.g.,0.25 mm and 0.15 mm).

FIG. 1C illustrates a revised target digital dental model 106 after IPRprescription according to one or more embodiments of the presentdisclosure. The revised target digital dental model 106 can be createdby modifying the digital dental model 100 and the target digital dentalmodel 104 according to the IPR prescribed at the determined position.

For example, the revised target digital dental model 106 can include adigital removal of the portion of the first tooth 101 and second tooth102 overlapping 103 in the target digital dental model 104 andidentified to be removed at the determined position. In someembodiments, the removed portion 103 can include a total ofapproximately 0.25 millimeters of the first tooth 101 and 0.25millimeters of the second tooth 102 for a total removed portion 103 ofapproximately 0.50 millimeters, for example. Such an amount of removalcan be beneficial for the cosmetic appearance and/or the structuralintegrity of the teeth 101,102 prescribed for IPR.

In various embodiments of the present disclosure, the treatment plan caninclude a plurality of stages. For example, at a determined position ofthe revised treatment plan a number of additional stages can be insertedinto the revised treatment plan.

A first additional stage can include removing an overlap of the firsttooth 101 and the second tooth 102. For example, the first additionalstage can include expanding the arch of the first tooth 101 and thesecond tooth 102. The expansion can include digitally changing a mesialposition or distal position of at least one tooth of the first tooth 101and the second tooth 102, among others. A second additional stage caninclude aligning the first tooth 101 and the second tooth 102 for IPR.

In various embodiments, the process can include reclining the firsttooth 101 and the second tooth 102 to a revised target position in therevised target digital model 106 after IPR prescription. In variousembodiments, a number of teeth without overlap can be reclined to arevised target position in the revised target digital dental model 106after IPR prescription.

In some embodiments, the target digital dental model 104 and revisedtarget digital dental model 106 can reflect an intermediate toothmovement within a treatment plan. Such a tooth movement may be usefulduring a particular process within the treatment plan (e.g., IPR,extraction, etc.).

In some embodiments, the digital dental model 100, target digital dentalmodel 104, and the revised target digital dental model 106 can bedisplayed via a user interface in three dimensions.

FIGS. 2A-2C illustrate examples of a reference line on each of a firsttooth and a second tooth. In various embodiments of the presentdisclosure, a reference line on each of the first tooth and the secondtooth can be identified.

FIGS. 2A-2B illustrate examples of a ridge endpoint reference line216-1, 216-2, 218-1, 218-2 on each of a first tooth 208 and a secondtooth 210 according to one or more embodiments of the presentdisclosure. The first tooth 208 and the second tooth 210 can be among anumber of teeth 208, 210, 212, and 214 in a treatment plan.

In one or more embodiments, a reference line can be identified on eachof the first tooth 208 and the second tooth 210 by calculating thedistance difference between ridge endpoints of each of the first tooth208 and the second tooth 210 at the determined position 209 of eachtooth and at the target position 211 of each tooth. For example, thedistance 216-1 between the ridge endpoints of the first tooth 208 andthe second tooth 210 at the determined position 209 and the distance216-2 at the target position 211 can be measured. The distance 216-1 atthe determined position 209 minus the distance 216-2 at the targetposition 211 can then be calculated.

In various embodiments of the present disclosure, the reference lines ofthe first tooth 208 and the second tooth 210 may be aligned if thedistance difference between the ridge endpoints at the determinedposition 209 and the target position 211 is within a thresholddifference. The threshold distance difference can be a distance that ispredetermined (e.g., by a treatment professional). For example, athreshold distance difference can be a distance of 0.75 millimeters.

Such a threshold may indicate that the teeth are aligned verticallyand/or laterally such that IPR can be performed. For instance, adistance difference threshold of 0.75 millimeters may result in theidentification and alignment of teeth that may be severely misalignedfor IPR if IPR is left to be performed at the end of the dentaltreatment. Teeth severely misaligned for IPR can include teeth thatwould be difficult or impossible for a treatment professional to performan IPR procedure on at the end of the dental treatment.

FIG. 2C illustrates an example 219 of a y-axis reference line 228, 226on each of a first tooth 220 and a second tooth 224 according to one ormore embodiments of the present disclosure. In one or more embodiments,a reference line 228, 226 can be identified on each of a first tooth 220and a second tooth 224 by calculating the y-axis of the first tooth 228and the y-axis of the second tooth 226. For example, the y-axis of thefirst tooth 228 and the second tooth 226 can include the mesial-distallocal axis of a tooth.

In various embodiments of the present disclosure, the y-axis referencelines 228, 226 of the first tooth 220 and the second tooth 224 may bealigned if the angle 230 between the y-axis of the first tooth 228 andthe y-axis of the second tooth 226 is within a threshold angle β. Thethreshold angle β can be an angle that is predetermined (e.g., by atreatment professional). For example, the threshold angle β may be 20degrees. Such a threshold may indicate that the teeth are alignedvertically and/or laterally such that IPR can be performed.

In various embodiments of the present disclosure, the reference lines ofthe first tooth 220 and the second tooth 224 may be aligned if the angle230 between the y-axis of the first tooth 228 and the y-axis of thesecond tooth 226 at a target position is greater than the angle 230 ofthe y-axis of the first tooth 228 and the y-axis of the second tooth 226at the determined position. For example, if the angle 230 at the targetposition is approximately 30 degrees and the angle 230 at the determinedposition is approximately 25 degrees, then the first tooth 220 and thesecond tooth 226 may be aligned for IPR at the determined position. Agreater y-axis angle at the target position may indicate that the teethare aligned vertically and/or laterally such that IPR can be performed.

In some embodiments of the present disclosure, the reference lines ofthe first tooth and second tooth may be aligned if the calculateddifference between the ridge endpoints of the first tooth and the secondtooth at the determined position and the target position is within athreshold distance, if the angle between the first tooth and the secondtooth at the determined position is within a threshold angle, or if thecalculated angle between the y-axis of the first tooth and the secondtooth at the target position is greater than the calculated angle at thedetermined position, or any combination thereof. The combination mayindicate that the teeth are aligned vertically and/or laterally suchthat IPR can be performed. For example, the combination may result inmore accurate identification and alignment of teeth that may be severelymisaligned for an IPR procedure if IPR is left to be performed at theend of the dental treatment.

FIG. 3 is a flow chart illustrating an example of a process 332 for IPRplanning according to one or more embodiments of the present disclosure.At 334, a digital dental model can be created from data received. Forexample, a digital dental model can be created from a scan of apatient's dentition and provided with computer-aided design and/ormanufacturing systems, including tooth-treatment systems.

The digital dental model can include data for a number of teeth. Thedigital dental model can include an initial digital dental model or anintermediate position of a digital dental model, for example.

At 336, a treatment plan can be computed from the digital dental model.The treatment plan can include moving a number of teeth to a targetposition of the treatment plan. In various embodiments of the presentdisclosure, the treatment plan can include a plurality of stages.

At 338, a determination can be made as to whether a first tooth overlapswith a second tooth in the target position. A first tooth overlappingwith a second tooth can include a potential collision in the targetposition with a neighboring tooth. In various embodiments of the presentdisclosure, the first tooth that overlaps with the second tooth can beoverlapping with a number of teeth on different sides of the firsttooth.

In response to no identified overlapping teeth in the target position,at 348, the process 332 can identify that IPR planning may not berequired.

In response to determining that a first tooth overlaps with a secondtooth, at 340, a determination can be made as to whether the first toothand the second tooth are misaligned for IPR in the initial position.Misalignment in the initial position can include no access for atreatment professional to perform IPR. For example, the distance betweenthe IPR region of the first tooth and the IPR region of the second toothmay be too small for a treatment professional to perform IPR.

In response to a determination that the teeth are not misaligned for IPRin the initial position, at 346, IPR can be prescribed in the initialposition. In response to a determination that the teeth are misalignedfor IPR in the initial position, the treatment plan can be revised. At342, a stage can be identified or a stage can be added in the treatmentplan wherein the reference line of the first tooth and the referenceline of the second tooth are aligned and the teeth are not colliding. At344, IPR can be prescribed on the first tooth and the second tooth atthe identified or added stage.

FIG. 4 illustrates an example of a method 492 for IPR planning accordingto one or more embodiments of the present disclosure. At 494, a firsttooth and a second tooth with an overlap in a target position of atreatment plan can be identified in a digital dental model. For example,an overlap can include a calculated overlap or a potential collision ina target position with a neighboring tooth.

In various embodiments of the present disclosure, an overlap between afirst tooth and a second tooth can be disregarded wherein the firsttooth and the second tooth are at least one of a molar and/or apremolar. Disregarding molars and/or premolars can include not aligningthe identified overlapping molars and/or premolars for IPR and notplanning IPR for the overlapping molars and/or premolars. For example,an overlapping molar and/or premolar can include an overlap between afirst molar and a second molar, an overlap between a first molar and afirst premolar, and an overlap between a first premolar and a secondpremolar.

At 496, a reference line can be identified for each of the first toothand the second tooth. In various embodiments, a reference line caninclude a distance between the ridge endpoints of each of the firsttooth and the second tooth. In various embodiments, a reference line caninclude a y-axis of each of the first tooth and the second tooth. Ay-axis of each tooth can include a mesial-distal local axis of thetooth, for example.

A reference line between the ridge endpoints of each of a first toothand a second tooth can be used on teeth with well defined ridges invarious embodiments of the present disclosure. For example, a ridgeendpoint reference line may be determined on incisor and/or canineteeth, and a ridge endpoint reference line may not be suitable on molarand/or premolar teeth.

At 498, a position of each of the first tooth and the second tooth isdetermined in which the reference line of the first tooth and thereference line of the second tooth are aligned and not overlapping.

At 499, IPR can be prescribed based on the determined position of eachof the first tooth and the second tooth. For example, IPR prescriptioncan include indicating in a treatment plan that an IPR procedure is tobe done at a particular stage of the plan based on this analysis.

FIG. 5 illustrates an example of a system 550 for IPR planning accordingto one or more embodiments of the present disclosure. In the system 550in FIG. 5, the system 550 includes a computing device 552 having anumber of components coupled thereto. The computing device 552 includesa processor 554 and a memory 556. The memory 556 can have various typesof information including data 558 and executable instructions 560, asdiscussed herein.

The processor 554 can execute instructions 560 that are stored on aninternal or external non-transitory computer device readable medium(CRM). A non-transitory CRM, as used herein, can include volatile and/ornon-volatile memory. Volatile memory can include memory that dependsupon power to store information, such as various types of dynamic randomaccess memory (DRAM), among others. Non-volatile memory can includememory that does not depend upon power to store information.

Memory 556 and/or the processor 554 may be located on the computingdevice 552 or off the computing device 552, in some embodiments. Assuch, as illustrated in the embodiment of FIG. 5, a system 550 caninclude a network interface 562. Such an interface 562 can allow forprocessing on another networked computing device, can be used to obtaininformation about the patient, and/or can be used to obtain data and/orexecutable instructions for use with various embodiments providedherein.

As illustrated in the embodiment of FIG. 5, a system 550 can include oneor more input and/or output interfaces 580. Such interfaces 580 can beused to connect the computing device 552 with one or more input and/oroutput devices 582, 584, 586, 588, and 590.

For example, in the embodiments illustrated in FIG. 5, the system 550can include connectivity to a scanning device 582, a camera dock 584, aninput device 586 (e.g. a mouse, a keyboard, etc.), a display device 588(e.g., a monitor), a printer 590, and/or one or more other inputdevices. The input/output interface 580 can receive executableinstructions and/or data, storable in the data storage device (e.g.,memory 556), representing a digital dental model, target digital dentalmodel, and/or a revised target digital dental model of a patient'sdentition.

In some embodiments, the scanning device 582 can be configured to scanone or more physical molds of a patient's dentition. In one or moreembodiments, the scanning device 582 can be configured to scan thepatient's dentition directly. The scanning device 582 can be configuredto input data into the computing device 552.

In some embodiments, the camera dock 584 can receive an input from animaging device (e.g., a two-dimensional or three-dimensional imagingdevice) such as a digital camera, a printed photograph scanner, or othersuitable imaging device. The input from the imaging device can, forexample, be stored in memory 556.

The processor 554 can execute instructions to provide a visualindication of a treatment plan and/or provided stage for IPR planning onthe display 588. The computing device 550 can be configured to allow atreatment professional or other user to input treatment goals. Inputreceived can be sent to the processor 554 as data and/or can be storedin memory 556.

Such connectivity can allow for the input and/or output of data and/orinstructions among other types of information. Although some embodimentsmay be distributed among various computing devices within one or morenetworks, such systems as illustrated in FIG. 5, can be beneficial inallowing for the capture, calculation, and/or analysis of informationdiscussed herein.

The processor 554, in association with the data storage device (e.g.,memory 556), can be associated with data 558. The processor 454, inassociation with the memory 456, can store and/or utilize data 558and/or execute instructions 560 for IPR planning. Such data 558 caninclude the digital dental model, target digital dental model, and/orthe revised target digital dental model.

The processor 554 coupled to the memory 556 can analyze a target digitaldental model of a treatment plan, including tooth data for a number ofteeth, to identify if a first tooth in the number of teeth overlaps witha neighboring tooth along an arch of the target digital dental model.The overlap can include a collision of a first tooth and a second toothin a target position within a target digital dental model, for example.

The processor 554 coupled to the memory 556 can revise the treatmentplan to remove the overlap and align the first tooth and neighboringtooth for IPR, prescribe IPR on the first tooth and the neighboringtooth in the aligned position, and recline the first tooth and theneighboring tooth to a revised target position in a revised targetdigital dental model after IPR prescription. Removing the overlap caninclude expanding the arch by digitally changing a mesial position or adistal position of at least one tooth of the first tooth and theneighboring tooth, among many others. Prescription of IPR can include anotification of the aligned position and a digital representation of theregion of the first tooth and the second tooth removed by the IPRprocedure prescribed, for example.

In various embodiments of the present disclosure, the processor 554coupled to the memory 556 can recline a number of teeth withoutundesired overlap in the digital dental model to the revised targetposition in the revised target digital dental model after IPRprescription.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art will appreciate that anyarrangement calculated to achieve the same techniques can be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments of thedisclosure.

It is to be understood that the above description has been made in anillustrative fashion, and not a restrictive one. Combination of theabove embodiments, and other embodiments not specifically describedherein will be apparent to those of skill in the art upon reviewing theabove description.

The scope of the various embodiments of the disclosure includes anyother applications in which the above structures and methods are used.Therefore, the scope of various embodiments of the disclosure should bedetermined with reference to the appended claims, along with the fullrange of equivalents to which such claims are entitled.

In the foregoing Detailed Description, various features are groupedtogether in example embodiments illustrated in the figures for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the embodiments of thedisclosure require more features than are expressly recited in eachclaim.

Rather, as the following claims reflect, inventive subject matter liesin less than all features of a single disclosed embodiment. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

The invention claimed is:
 1. A computing device implemented method forinterproximal reduction (IPR) planning, comprising: identifying a firsttooth and a second tooth within a set of teeth representing one dentalarch of a patient in a digital dental model wherein the first and secondtooth are adjacent on the arch and overlap at a target position of eachtooth during a treatment plan; identifying a mesial-distal referenceline of the first tooth and a mesial-distal reference line of the secondtooth; calculating an angle between the mesial-distal reference line ofthe first tooth and the mesial-distal reference line of the second toothat a provided stage of the treatment plan; revising the treatment planusing a computing device to provide an intermediate position for thefirst and second tooth, wherein: the mesial-distal reference line of thefirst tooth and the mesial-distal reference line of the second tooth arealigned sufficiently for IPR to be performed based on the calculatedangle between the mesial-distal reference line of the first tooth andthe mesial-distal reference line of the second tooth being within aspecified threshold; and wherein the first and second tooth are notoverlapping such that IPR can be performed on at least one of the firstand second tooth.
 2. The method of claim 1, including determining theintermediate position of each of the first tooth and the second toothincluding calculating a distance difference between ridge endpoints ofeach of the first tooth and the second tooth at the intermediateposition and at the target position.
 3. The method of claim 2, whereinthe mesial-distal reference line of the first tooth and themesial-distal reference line of the second tooth are aligned when thecalculated difference between the mesial-distal reference line of thefirst tooth and the mesial-distal reference line of the second tooth atthe intermediate position and at the target position are within athreshold distance.
 4. The method of claim 1, including determining theintermediate position of each of the first tooth and the second toothbased on the calculated angle between the mesial-distal reference lineof the first tooth and the mesial-distal reference line of the secondtooth at the intermediate position of each of the first tooth and secondtooth.
 5. The method of claim 4, wherein in the mesial-distal referenceline of the first tooth and the mesial-distal reference line of thesecond tooth are aligned if the calculated angle between themesial-distal reference line of the first tooth and the second tooth atthe intermediate position is within a threshold angle.
 6. The method ofclaim 1, including determining the intermediate position of each of thefirst tooth and the second tooth based on the calculated angle betweenthe mesial-distal reference line of the first tooth and the second toothat the intermediate positions and at the target position.
 7. The methodof claim 6, wherein the mesial-distal reference line of the first toothand the mesial-distal reference line of the second tooth are alignedwhen the calculated angle at the target position is greater than thecalculated angle at the intermediate position.
 8. The method of claim 1,wherein the method further includes disregarding an overlap between afirst tooth and a second tooth in the target position, wherein the firsttooth and the second tooth are at least one of a molar and a premolar.9. A system for interproximal reduction (IPR) planning, comprising: aprocessor; and a memory coupled to the processor and configured todirect the processor to: analyze a target digital dental model of atreatment plan, including tooth data for a number of teeth within a setof teeth representing one dental arch of a patient, to identify when afirst tooth in the number of teeth overlaps with a neighboring toothwithin the set of teeth representing one dental arch of a patient;calculate an angle between a mesial-distal reference line of the firsttooth and a mesial-distal reference line of the neighboring tooth at aprovided stage of the treatment plan; and in response to anidentification that the first tooth overlaps with the neighboring toothof the target digital dental model, revise the treatment plan to: removethe overlap and align the first tooth and the neighboring tooth in anintermediate position within the treatment plan in which themesial-distal reference line of the first tooth and the mesial-distalreference line of the neighboring tooth are aligned sufficiently for IPRto be performed on at least one of the first and neighboring tooth, andbased on the calculated angle between the mesial-distal reference lineof the first tooth and the mesial-distal reference line of theneighboring tooth being within a specified threshold; prescribe IPR onthe first tooth and the neighboring tooth in the intermediate position;and recline the first tooth and the neighboring tooth to a revisedtarget position in a revised target digital dental model after IPRprescription.
 10. The system of claim 9, wherein the memory furtherdirects the processor to identify the first tooth in the number of teeththat overlaps with a number of neighboring teeth on different sides ofthe first tooth.
 11. The system of claim 9, wherein the memory furtherdirects the processor to a change a mesial position of at least onetooth of the first tooth and the neighboring tooth to remove the overlapof the teeth.
 12. The system of claim 9, wherein the memory furtherdirects the processor to change a distal position of at least one toothof the first tooth and the neighboring tooth to remove the overlap ofthe teeth.
 13. The system of claim 9, wherein the memory further directsthe processor to recline a number of teeth without undesired overlap inthe target digital dental model to a revised target position in therevised target digital dental model after IPR prescription.
 14. Anon-transitory computing device readable medium having executableinstructions that can be executed by a processor to cause a computingdevice to perform a method for interproximal reduction (IPR) planning,comprising: computing a treatment plan for moving a number of teethwithin a set of teeth representing one dental arch of a patient to atarget position; identifying a first tooth in the number of teeth havinga potential collision in the target position with a neighboring tooth;detecting misalignment for IPR of the first tooth and the neighboringtooth in an initial position of the first tooth and the neighboringtooth; calculating an angle between a mesial-distal reference line ofthe first tooth and a mesial-distal reference line of the neighboringtooth at a provided stage of the treatment plan; and revising thetreatment plan to: provide a stage including an intermediate positionwithin the treatment plan of the first tooth and the neighboring toothin which the mesial-distal reference line of the first tooth and themesial-distal reference line of the neighboring tooth are alignedsufficiently for IPR to be performed on at least one of the first andneighboring tooth and the first tooth and the neighboring tooth do notcollide based on the calculated angle between the mesial-distalreference line of the first tooth and the mesial-distal reference lineof the neighboring tooth being within a specified threshold; andprescribing IPR on the first tooth and the neighboring tooth at theprovided stage.
 15. The non-transitory computing device readable mediumof claim 14, wherein the instructions can further be executed to performthe method including providing the stage of the treatment plan bycomputing a distance difference between a ridge of the first tooth and aridge of the neighboring tooth at the provided stage and at the targetposition, wherein the mesial-distal reference lines are aligned if thedifference is approximately 0.75 millimeters or less.
 16. Thenon-transitory computing device readable medium of claim 14, wherein themesial-distal reference lines are aligned when the calculated angle isapproximately 20 degrees or less.
 17. The non-transitory computingdevice readable medium of claim 14, wherein the instructions can furtherbe executed to perform the method including providing the stage of thetreatment plan by computing the difference of an angle between themesial-distal reference line of the first tooth and the mesial-distalreference line of the neighboring tooth at the provided stage and anangle between the mesial-distal reference line of the first tooth andthe mesial-distal reference line of the neighboring tooth at the targetposition.
 18. The non-transitory computing device readable medium ofclaim 14, wherein the instructions can be executed to compute aplurality of stages in the treatment plan.
 19. The non-transitorycomputing device readable medium of claim 18, wherein the instructionscan be executed to insert a number of sub-stages at the provided stageof the treatment plan, wherein a first sub-stage of the number ofsub-stages includes expanding the arch of the first tooth and theneighboring tooth.
 20. The non-transitory computing device readablemedium of claim 18, wherein the instructions can be executed to insert asecond sub-stage in the treatment plan, wherein the second sub-stageincludes aligning the first tooth and neighboring tooth for IPR.